A small, but in my opinion significant, percentage of programming questions (not math questions that'd belong on https://math.stackexchange.com/) and some of their answers require mathematical formulas.

Some mathematical formulas are nearly incomprehensible when approximated in ASCII plain text. Some authors instead use LaTeX code blocks in their posts, but not every one knows how to read those:

But this can only be taken so far. As soon as matrices or vectors with their components are involved (which can happen for programming questions that do not belong on https://math.stackexchange.com/), this approach breaks down.

But would it be possible to simply allow posts (at least questions and answers, maybe also comments and tag wikis) to contain MathML markup? For browsers that don't yet support it, one of the available polyfills could be used. If client-side performance is of concern, the polyfill could only be referenced when the Stack Overflow server detects the string <math> in the content (which shouldn't affect server-side performance too much, I think).

Aww, the gyrations those mathematicians have to go through to be understood. We can just post a code snippet.
– Hans PassantMar 2 '16 at 23:03

@HansPassant Well, sometimes we get question of the pattern: "To compute $formula_A, I've written $code_snippet_B. However, while according to my manual calculation, $formula_A gives result $D for input $C, $code_snipped_B's output for $C is $E. I suspect that $language_F's foo-operator differs from the mathematical foo notion, but can't find any hint toward that in the documentation."
– das-gMar 2 '16 at 23:11

In my experience, the extent of the mathematical notation that needs to be posted on Stack Overflow can be handled adequately by Unicode characters. How often are you really answering on-topic questions with long mathematical diatribes about matrices and vectors? And how often would it not be better just to express the solution in terms of executable code, which is how the asker will inevitably need to transform your abstract mathematical notation?
– Cody Gray♦Mar 3 '16 at 10:26

1

Yeah, for answers it indeed isn't that important, @CodyGray. But for Questions, expressing what you want to do separately from how you tried it to do can be very useful.
– das-gMar 3 '16 at 10:28